1. Field of the Invention
The present invention relates to an information recording medium such as a sheet of paper which records, as an optically readable code pattern, so-called multimedia information including audio information such as voice and music, video information obtained from, e.g., cameras and video apparatuses, and digital code data obtained from personal computers and wordprocessors, and also relates to an information reproduction apparatus for optically reading the code pattern recorded in such an information recording medium and reproducing the original multimedia information.
2. Description of the Related Art
Conventionally, various media such as magnetic tapes and optical disks are known as media for recording voice, music, and the like information. Unfortunately, the unit costs of these media are relatively high even if a large quantity of copies of them are made, and the media require a large spare for keeping them. Furthermore, if it is necessary to deliver a medium recording voice to another person in a remote place, the delivery requires much labor and time regardless of whether the medium is mailed or directly brought. This similarly applies to all kinds of so-called multimedia information, other than audio information, which includes video information obtained from, e.g., cameras and video apparatuses and digital code data obtained from, e.g., personal computers and wordprocessors.
The inventor team including the present inventor therefore invented a system for recording multimedia information, which includes at least one of audio information, video information, and digital code data, in an information recording medium such as a sheet of paper in the form of a dot code as image information, i.e., coded information which can be transmitted by a facsimile apparatus and a large quantity of copies of which can be inexpensively made, and also invented a system for reproducing the information. This invention was described and claimed in International Application No. PCT/JP93/01377 (U.S. Ser. No. 08/407,018) and internationally published in Apr. 14, 1994, as International Publication No. WO94/08314.
A dot code disclosed in the above international application comprises a group of a plurality of blocks arranged in a matrix manner. Each block has a data dot pattern including a plurality of dots arranged in accordance with the contents of data and a block address pattern which is arranged to have a predetermined positional relationship with the data dot pattern and indicates the address of the block.
That is, as illustrated in FIG. 1A, each block is constituted by a marker 10, an array direction detecting code 12, a block address 14, and block recorded data 16. The markers 10 are recorded as large circular dots, and the block recorded data 16 is constituted by an array of dots far smaller than the markers 10 (for example, the dot diameter of the data 16 is 1/7 the diameter of the marker dot).
These blocks are two-dimensionally arranged to form a dot code as illustrated in FIG. 1B. In FIG. 1B, this dot code is formed by two blocks in the vertical direction and N/2 blocks in the horizontal direction. Data reproduced from all of these two-dimensionally arranged blocks is reproduced as one code. Note that the block addresses 14 represent numbers 1 to N such as indicated by BLOCK 1, BLOCK 2, BLOCK 3, . . . , BLOCK N in FIG. 1B. Note also that each block has a vertical size (block width BW) and a horizontal size (block length BL), and a 2-block vertical size corresponds to the width of a dot code, which is called an effective code width CEW.
FIG. 1C shows the arrangement in FIG. 1B in a simplified form only by describing the block addresses 14.
The above international application of this information reproduction system has disclosed a method in which an information reproduction apparatus for optically reading and reproducing such a dot code recorded on an information recording medium is held in an operator's hand and manually scanned on the recording medium along the recorded dot code to thereby read the dot code.
FIG. 2A illustrates an example of the shape of this reader. As in FIG. 2A, it is possible to hold a reader 20 in an operator's hand such that the reader 20 is perpendicular to a dot code 18, i.e., the surface of a recording medium, and to scan the reader 20 in the longitudinal direction of the dot code 18. In this case the dot code 18 can be read regardless of the scanning direction because the block addresses 14 are written in the dot code as described above. That is, information recorded as the dot code 18 can be reproduced by manually scanning the reader 20 from one end to the other of the dot code 18.
In performing this manual scanning, a scanning position indication mark 22 can be formed on the reader 20, as an index, by which the reader 20 is scanned along the dot code 18. Examples of this scanning position indication mark 22 are an indication mark corresponding to the width of the dot code 18, FIG. 2A, the left side, and an indication mark indicative of the center of the reader 20, FIG. 2A, the right side.
This scanning position indication mark 22 allows an operator to scan the reader 20, while taking account of the width of the dot code 18, or along the center of the dot code 18, by seeing the scanning position indication mark 22. This makes a correct scanning along the dot code 18 feasible.
In practice, however, as illustrated in FIG. 2B, when the reader 20 is manually scanned on the dot code 18 from the left end to the right end the scan may sometimes be zigzagged by a shake as indicated by a scan locus 24. This produces a code portion 26 which is not read during the scan. This zigzag amount, i.e., a scan shake maximum value v.sub.max is at most a few hundred microns in the case of a mechanical automatic scan. However, in the manual scan case this value can be 2 to 3 mm although it depends upon an individual difference.
As shown in FIG. 2C, assuming the width of the dot code 18 is a code width CW, the horizontal size of an imaging area 28 is an imaging length GV, and the vertical size of the imaging area 28 is an imaging width GH, the allowable amount, A, of this shake is given by ##EQU1## Note that this equation holds when the code width CW is the same as the effective code width CEW.
Also, as shown in FIG. 2D, when the scan is manually done the imaging area 28 is in some instances rotated during imaging. In this case the allowable amount A becomes smaller than that in the case of FIG. 2C and is given by ##EQU2## where G'H is the effective imaging width given by EQU G'H=GH.times.cos(.theta.)-GV.times.sin(.theta.)
Furthermore, the code portion 26 which is not read during the scan is sometimes produced by some other reasons than the shake. That is, as shown in FIG. 2B, not the entire bottom surface (i.e., an area 30 in which the casing of the reader covers the paper surface) of the reader 20 is the imaging area 28. Accordingly, if at the start of the scan the operator sets the reader 20 at the left end of the dot code 18, i.e., holds the reader 20 such that the casing of the reader 20 covers the dot code 18, the imaging area 28 does not image the left end of the dot code 18 in some cases. Consequently, the code portion 26 which is not read during the scan is produced on the scan start end of the dot code 18. Similarly, at the end of the scan, i.e., when the operator manually scans the reader 20 from the left end to the right and stops the reader at the right end, a code portion at the right end is sometimes left unread without being imaged. That is, the code portion 26 which is not read during the scan takes place at the scan termination end of the dot code 18.